Militants in Nigeria release 6 hostages, including 5 South Korean oil field workers

(AP) Militants freed one Nigerian and five South Korean oil field workers Thursday, letting the hostages go at the request of a jailed rebel leader.

The workers arrived by car at the office of the regional governor in the southern oil hub of Port Harcourt late Thursday, a day after gunmen kidnapped them from a natural gas plant during the latest attack on the African nation's oil industry.

The Movement for the Emancipation of the Niger Delta first said they would free the hostages only if the government released Mujahid Dokubo-Asari, a prominent militant jailed last year on treason charges.

But the group said Dokubo-Asari, an ethnic Ijaw who wants autonomy for the southern region around the oil-rich Niger River delta region, asked that the detainees be released. It was not clear how or where Dokubo-Asari made the appeal.

The militants are waging a violent campaign to press demands for the redistribution of Nigeria's oil wealth, saying people in the oil region don't receive a fair share. The group has staged a wave of attacks and hostage takings across the area this year.

The hostages were contract workers at a gas plant run by Royal Dutch Shell PLC's Nigerian subsidiary near Port Harcourt. Shell said it has shut down the plant, which has capacity of 150 million cubic feet of gas a day.

South Korea's Foreign Ministry said three of the kidnapped South Koreans work for Daewoo Engineering and Construction Co. and the other two for Korea Gas Corp.

The militants said Wednesday that they would target "facilities of crucial importance to the oil industry" in more attacks in the next few weeks. "Oil companies in the Niger Delta are again warned to leave while they can."

Nigeria is Africa's biggest oil exporter and the United States' fifth-largest supplier, usually exporting 2.5 million barrels daily. Attacks on oil pipelines and kidnappings have cut oil production by more than 20 percent this year, adding to the upward pressure on world prices.